1. Field of the Invention
This invention relates to a platform support device for lifting loads or individuals over the height of a structure, especially for performing work on said structure, this device comprising, in combination with a platform, platform lifting elements of the hoist type for controlling the raising level of the platform as required, combinable modular components forming the mast for reaching a desired height, each mast element being installed from the load platform that can be connected to the masts on the one hand by hoist-type lifting elements that can be disconnected from said masts as required, and on the other hand by means for temporarily immobilizing the platform relative to a modular element of each mast to allow the addition or the removal of at least one modular element at the top of the masts depending on the desired raising height of the platform, with the platform immobilized.
2. Description of the Related Art
Working over the height of facades of structures of great height is usually done using so-called suspended scaffolds. Such scaffolds are composed of a platform on which hoists are carried, the platform being suspended from the roof of the structure via fixed cables with parts connected to the roof. Such an approach is satisfactory when the roof is easily accessible and when it is possible to install anchoring elements of the cable and counterweights necessary for proper operation of the assembly. In the opposite case, the operators are powerless.
Another approach would be to position a lifting platform from the ground. However, no existing approaches are satisfactory, since they do not allow a great height to be reached in spite of using a hoist. Such is the case of the scaffolding described in the patent FR-A-2,624,173. This document describes a scaffolding of the type comprising at least one essentially vertical mast that is supported, on the one hand, on an essentially horizontal surface and, on the other hand, on an essentially vertical surface, the mast being used to anchor the cable of a hoist suited to raising or lowering, over the height of a mast, a sliding sleeve that belongs to a bracket supporting a working platform. Besides the fact that the installation of the masts is not addressed in this document, it is stated that the position of the masts that extend along one longitudinal edge of the platform comprises a limitation on the raising of the platform because they must necessarily be joined to the facade of the structure to prevent any overturning of the assembly of the structure. Thus, in this document, the masts are connected by the anchor piece shown at 9 in the figures, this anchor piece indicating the end of raising of the platform and making it impossible to use such a scaffolding for working at great heights.
The system described in the patent U.S. Pat. No. 3,323,616 is composed of a platform moving along two masts formed from telescoping modular elements requiring assembly or respectively disassembly of two masts simultaneously. Again, a sleeve belonging to a bracket supporting the working platform slides along the mast, making impossible any anchoring of the mast to the facade and necessitating synchronous movement of the platforms. Since this system cannot include means allowing its attachment to a facade, this system is not suited to working at great heights.
The system described by the patent U.S. Pat. No. 3,612,219 is composed of two ladders and one platform. The ladders are cross-braced to allow them to be kept in the upright state, thus making independent disassembly impossible from one of the ladders. The platform that is raised by the hoists carried on the platform is not guided along the ladders, making such a system unsuited for raising to great heights.
The patent FR-A-625,646 describes scaffolding whose platform is carried by independent masts that can be attached to a facade by means of buttresses. In this case, the platform is formed again by a bracket and two sleeves that each slide along a mast as shown in FIG. 1 of this patent or in the passage column 2—lines 19 to 26 of the description. Said buttresses thus constitute an obstacle to the lowering of the platform that can only be completely lowered when the masts are dismantled and the buttresses are removed. This approach therefore prevents free raising and lowering of the platform along the masts. Moreover, the platform/mast link using a sliding sleeve in the case of a structure with three masts requires synchronous movement of the entire platform.
The patent EP-A-612,899 describes a plate attached to two ladders by means of pivoting hooks hanging on the rungs of said ladders. This device allows raising and lowering of the platform along the masts, this movement being controlled by means of a hoist from within the platform or from the ground. However, the system of guiding the platform along the uprights of the ladders is not described here. During vertical movement, the platform is also made free to move horizontally, which makes this system dangerous and unsuited to working at great heights. Moreover, since the ladders are made integral by the diagonals, one of the ladders cannot be removed without removing the other.
Thus, the documents that are discussed above do not describe scaffolding that can be used at great heights, of which the platform could be moved vertically over the entire height of the uprights without adversely affecting the safety of the assembly. Moreover, none of these documents describes a device allowing asynchronous movement of two plates along two guide surfaces of the same mast.